Distributed-cache-memory storage apparatuses that support a REC consistency mode function in which order is preserved, which is one type of advanced copy, to perform a backup and mirroring between redundant array of independent disks (RAID) devices have been proposed. Advanced copy indicates the function of copying data of a storage apparatus at a point in time (source volume) and generating another volume (copy volume) within the same storage apparatus.
Remote mirroring may operate in synchronous mode and asynchronous mode. In synchronous mode, no completion acknowledgement to a write request is made until writing of data to a target has been completed. In asynchronous mode, a completion acknowledgement to a write request is made without waiting for the completion of writing of data to a target. Generally, asynchronous mode may be classified into consistency mode for remote mirroring and stack mode for remote backup. In consistency mode, order of writing data is preserved.
REC mode is known in itself. For example, in that mode, mirroring can be performed in accordance with commands, such as Start, Stop, Suspend, Forced Stop, Forced Suspend, and Resume. A Start command causes generation of a mirrored volume and a synchronous process to start. A Stop command causes cancellation of mirroring, discarding a mirrored volume, and transferring all data written before the Stop command is issued to a copy volume until the Stop command ends. A Suspend command causes cancellation of mirroring, maintaining a mirrored volume, and transferring all data written before the Suspend command is issued to a copy volume until the Suspend command ends. The maintained mirrored volume can be resynchronized in response to a Resume command. A Forced Stop command causes cancellation of mirroring and discarding a mirrored volume. It is unnecessary to transfer data written before the Forced Stop command is issued to a copy volume. A Forced Suspend command causes cancellation of mirroring and maintaining a mirrored volume. It is unnecessary to transfer data written before the Forced Suspend command is issued to a copy volume. The maintained mirrored volume can be resynchronized in response to a Resume command. A Resume command causes resynchronization after a Suspend command. The resynchronization is performed by transferring data written in a suspended state.
FIG. 1 illustrates one example of a traditional distributed-cache-memory storage apparatus. In FIG. 1, a storage apparatus 1 includes a copy-source storage device (hereinafter referred to also as a copy-source device) 3-1 and a copy-target storage device (hereinafter referred to also as a copy-target device) 3-2 connected to each other over a network 2. Each of the copy-source device 3-1 and the copy-target device 3-2 can include a plurality of control modules 11, for example. Each of the control modules 11 includes a processor (e.g., a central processing unit (CPU)), a buffer 12 for use in recording, and a disk unit 13.
The storage apparatus 1 illustrated in FIG. 1 performs a process for reading and/or writing (hereinafter referred to simply as reading/writing) logical volume data for each control module 11. For example, like with the REC consistency mode function in which order is preserved, when order of writing data in remote copying in asynchronous mode is preserved, data stored in a disk in the disk unit 13 in the copy-source device 3-1 is stored in the buffer 12 in the copy-source device 3-1, and if the buffer 12 becomes full or a predetermined period of time elapses since storing data is started, the data in the buffer 12 in the copy-source device 3-1 is collectively transmitted to the copy-target device 3-2, which is connected to the copy-source device 3-1 via the network 2. In the copy-target device 3-2, when all data has been received, the data stored in the buffer 12 for use in recording is collectively developed and stored in a disk in the disk unit 13. Accordingly, in order to perform the REC consistency mode function, it is necessary to set the buffer 12 in each of the copy-source device 3-1 and the copy-target device 3-2.
FIGS. 2A, 2B, 2C, 2D and 2E illustrate an example procedure for newly setting a buffer region in the buffer 12 for use in the REC consistency mode. FIG. 2A illustrates a state in which three storage devices 3-1, 3-2 and 3-3 are prepared by way of example to perform the REC consistency mode function. FIG. 2B illustrates a state in which the storage devices 3-1, 3-2 and 3-3 are connected together via a cable or network 5. For the sake of convenience of description, the storage devices 3-1 and 3-2 form a group G1, and the storage devices 3-1 and 3-3 form a group G2. FIG. 2C illustrates a state in which routing by which each of the storage devices 3-1 to 3-3 will be connected to a counterpart storage device is set from a storage management personal computer (PC) 6 for each of the storage devices 3-1 to 3-3. FIG. 2D illustrates a state in which the newly setting of the buffer 12 for the group G1 in order to perform the REC consistency mode function is executed from the storage management PC 6 for each of the storage devices 3-1 and 3-2. FIG. 2E illustrates a state in which the newly setting of the buffer 12 for the group G2 in order to perform the REC consistency mode function is executed from the storage management PC 6 for each of the storage devices 3-1 and 3-3.
In such a way, the newly setting of the buffer 12 is executed in each of the copy-source device 3-1 and the copy-target devices 3-2 and 3-3 from their respective storage management PCs 6. Accordingly, the newly setting of the buffer 12 is executed in each of the copy-source device 3-1 and the copy-target devices 3-2 and 3-3. It is preferable that the copy-source device 3-1 and the copy-target devices 3-2 and 3-3 be connected to their respective storage management PCs 6.
Additionally, it is preferable that, because the newly setting is executed for each of the copy-source device 3-1 and the copy-target devices 3-2 and 3-3, in order to know whether the newly setting of the buffer 12 of a counterpart storage device is correct, the newly setting be checked from the storage management PC 6 for each of the copy-source device 3-1 and the copy-target devices 3-2 and 3-3. That is, the storage management PC 6 connected to the copy-source device 3-1 checks whether the newly setting of the buffer 12 of each of the copy-target devices 3-2 and 3-3, which are counterpart storage devices, is correct. The storage management PC 6 connected to each of the copy-target devices 3-2 and 3-3 checks whether the newly setting of the buffer 12 of the copy-source device 3-1, which is a counterpart storage device, is correct.
A traditional storage apparatus has drawbacks including a problem in that it is difficult to newly set a buffer for use in a function in which order of writing data in remote copying in asynchronous mode is preserved, like, for example, the REC consistency mode function.